MOSCOW - Russia on Tuesday accused unspecified external forces of seeking to undermine UN-Arab League peace envoy Kofi Annan's efforts to end more than a year of bloodshed in Syria, saying support for government foes was threatening a fragile ceasefire.

Russian Foreign Minister Sergei Lavrov suggested armed opponents of Syrian President Bashar Assad's government were largely to blame for persistent violence which has marred a ceasefire that began last week as part of Annan's six-point peace plan.

"There are those who want Kofi Annan's plan to fail," Lavrov said in televised remarks. "Today, those who ... from the beginning foretold the failure of Annan's plan are doing a lot to see to it that this prophecy comes true."

"They are doing this by delivering arms to the Syrian opposition and stimulating the activity of rebels who continue to attack both government facilities and ... civilian facilities on a daily basis," Lavrov said.

"Of course, government forces are also taking measures to react to such provocations, and as a result it is not all going very smoothly yet," said Lavrov, who called the ceasefire "quite fragile".

Russia has provided Syria with weapons and shielded Assad by blocking UN Security Council resolutions condemning his government for a crackdown in which the United Nations says its forces have killed more than 9,000 people since March 2011.

Russia has pledged its full support for Annan's peace plan and last week called on the Syrian government to step up implementation, but Moscow has also put much of the blame for the bloodshed on opposition forces.

Lavrov reiterated Russia's calls for foreign countries to press Assad's opponents to comply with Annan's plan, and its criticism of the "Friends of Syria" group of Western and Arab nations, which he said were undermining UN peace efforts.

"There are countries, there are external forces, that are not interested in the success of the current Security Council efforts, that are trying to replace the Security Council with informal formats such as the "Friends of Syria" group ... and are in all kinds of ways encouraging the Syrian opposition not to cooperate with the government in providing for a ceasefire and the subsequent establishment of dialogue," Lavrov said.

Syria has given post-Soviet Russia its firmest foothold in the Middle East, buying billions of dollars' worth of weapons and hosting a maintenance and supply facility that is Russia's only warm-water naval port outside the former Soviet Union.

Russia says it is not trying to protect Assad but that calls by foreign governments for his exit from power amount to unacceptable interference in Syrian affairs.